Termite acoustic detection

ABSTRACT

A method and system for detecting the presence of subterranean termites, involving use of a thermal imaging camera to scan the structure before installation of an acoustic sensor in order to quickly locate potential areas of subterranean termite infestation, and an acoustic sensor in the form of an accelerometer or the disclosed innovative acoustic sensors having a bandwidth of at least 100 Hz to 15 kHz to detect noises made by the subterranean termites. Information collected by the acoustic sensor may be transmitted to a portable mini-computer (pocket PC) for confirmation and to a central operations center for inclusion in a comprehensive database of termite data and information. A method and system for detecting the presence of dry-wood termites concealed in a structure, involving use of a heat source to warm up the wooden structure of interest and then using a thermal imaging camera to scan the structure for suspicious dry-wood infestation, followed by the use of an acoustic sensor and pattern recognition software to more precisely and accurately locate potential area of dry-wood termite infestation. Additionally, structural damage can be evaluated by the methods discussed herein, including live trees. Additionally, the method can be used to manipulate termite infestation behavior.

RELATED APPLICATIONS

This application is a continuation-in-part and claims the benefit under35 U.S.C. § 119(e) of U.S. Provisional Application Ser. No. 60/417,257filed Oct. 9, 2002, hereby specifically incorporated by reference in itsentirety

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

U.S. Department of Agriculture Award #58-6402-04-040

REFERENCE TO APPENDIX

The computer program listing appendix submitted on a compact disk ishereby incorporated by reference. Two duplicate copies of a single diskare included. The disk was made on Oct. 4, 2003.

FIELD OF THE INVENTION

This invention relates to insect detection and, more particularly, tomethods, systems and devices for detecting and preventing termitedamage.

DESCRIPTION OF RELATED ART

Termites are extremely destructive to wood material. Termites attack anddestroy wood almost everywhere in the world, with the exception ofclimate zones that experience hard freezing. There are close to fiftyspecies of termites in the United States, the majority of losses to woodmaterial being caused by subterranean species. All termites are socialinsects. They live in colonies that can number over one millionindividuals.

It is difficult to put a dollar amount estimate on termite damage.However, renowned termite scientist Dr. Nan Yao Su at the University ofFlorida has estimated that the total annual cost of termite control anddamage repair for the United States alone was $11 billion in 1999.

Few homes are treated for termite detection/prevention duringconstruction, although this is the best and most economical way toprevent termite attack. Untreated foundations make the house verysusceptible to termite attack. It is often very difficult and costly toapply effective control measures after a building has become infestedwith termites.

It is rarely apparent from visual observation that a termite infestationis active and that wood damage is occurring. Typically, only about 30percent of structural wood in a structure is visible for visualinspection. Even when visible wood is to be inspected, an inspectoroften has to rely on secondary signs of an infestation, such as moisturestaining, the presence of foraging tubes and debris expelled fromtermite colonies.

Another method often used to detect termites is to tap the surface ofthe wood while listening for a characteristic sound indicative of anunderlying gallery void. When a suspected area is located, the inspectorapplies a sharp probe, such as a screwdriver, to break the wood surfaceand locate wood galleries and live termites. This method has significantdisadvantages. The confirmation of an active infestation requires somelocalized damage to the wood. Also, when termites are exposed in thismanner, the destruction induces termites to retreat from the disturbedarea and may reduce the effectiveness of a subsequent localizedtreatment.

Commercial demand for a dependable, nondestructive and non-subjectivemethod to detect termites has spawned a number of alternatives to visualinspection. However, none of these techniques has satisfied thenon-destructive and non-subjective requirements, and many infestationsare still missed.

Prior devices for nondestructive detection of termites may be generallyclassified into four categories:

-   -   (1) Apparatus having sensors that detect the presence of gases        emitted by termites, as disclosed for example in U.S. Pat. No.        6,150,944;    -   (2) Apparatus having acoustic sensors that detect insect sounds        at high or ultrasonic frequencies, as disclosed for example in        U.S. Pat. No. 4,809,554 to Shade et al., U.S. Pat. No. 5,285,688        to Robbins et al., and Japanese Patent Application JP        H07-143837;    -   (3) Apparatus having sensors that detect destruction of a baited        sample, for example, inclusion of circuit elements designed to        be destroyed as the sample is destroyed, thereby breaking a        circuit, as disclosed in U.S. Pat. Nos. 6,052,066; 5,815,090;        5,592,774; activation of a switch by movement of a mechanical        element in response to sample destruction, as disclosed in U.S.        Pat. No. 5,571,967 and Japanese Patent Publication No.        H7-255344; or penetration of a film across the entrance to a        baited trap, as disclosed in U.S. Pat. No. 5,877,422; and    -   (4) Apparatus employing infrared sensors.

Detection devices that rely on sensing the presence of termite-createdgases eliminate the need to use bait to attract the termites, and, intheory, they can signal the actual locations of the termites. Asignificant disadvantage, however, is that the gases must be abstractedwithin a confined space, such as within the walls of a structure. Thesedevices are thus unsuitable for detecting termites in wood that is notwithin a confined space. Moreover, the use of these devices to detecttermites is very time-consuming and costly as a result.

Detection devises that rely on sensing ultrasonic termite sounds, on theother hand, offer the advantage that they can be placed on the exteriorof structural walls rather than within the walls. The ultrasonicfrequencies, however, are difficult to detect through walls and otherconcealing structures due to the signal's very short distance of travel(ultrasonic frequencies have very high transmission loss), and thisprocess fails to take into account the full range of termites noises,which fall primarily in the range of 100 Hz to 15 kHz.

An alternative to devices employing ultrasonic acoustic sensors is adevice employing sensor (or electronic stethoscope) arranged to detectacoustic signals and process them for listening and directsinterpretation by a trained operator. In some cases, the device may beconnected to a spectrum analyzer arranged to generate a plot of signalsin the frequency domain, which can then be interpreted by the operator.These devices require a high degree of operator skill. In addition, suchdevices typically use a relatively narrow frequency range. For example,the device disclosed in U.S. Pat. No. 4,895,025 is focused on afrequency range of 1462.5 Hz to 3337.5 Hz. The device of U.S. Pat. No.4,941,356 (the '356 patent), on the other hand, is evidently intended towork over a broad range of audible frequencies (100 Hz to 15 kHz). The'356 patent, however, fails to disclose specific apparatus, algorithmsor noise patterns useful for detection over the specified frequencyrange.

The various devices for sensing the destruction of bait sample areuseful for detecting the presence of termites in the vicinity of astructure, but cannot be used to locate precise areas of termiteinfestation in concealed areas within the structure. Once it has beendetermined that termites are present in the vicinity of the structure,the only way to determine the actual locations of termites within thestructure is to remove portions of the structure, which is, again,damaging and costly.

It has also been proposed to use infrared sensors to detect the surfacetemperature differences indicative of termite infestations. Infrareddetection works because subterranean termites require a high percentageof humidity in their living environment. Moisture brought in by thetermites produce a temperature change in the wall, which can be detectedby an infrared thermal imaging device. However, this is a relativelynonspecific method, yielding many, many false positives since there aremany sources of temperature differences in a typical structure, such asnon-uniform insulation material, air-conditioning ducts, leakage, airmovement through wall cracks, water and moisture problems, etc. As aresult, detection of termites using infrared sensors still requiresdestruction of walls to verify results and to more specifically locatethe actual termite infestations. Furthermore, use of infrared sensingfor detection of termites also requires a relatively high degree ofoperator skill, training and judgment which adds time and cost to itsuse.

Devices relying on acoustic detection appear to offer the bestcombination of accuracy and lack of destruction. Such devices, however,generally do not take into account the full range of termite sounds, asexplained above. Moreover, the design of prior devices has generallyresulted in only highly localized detection ability, therebynecessitating the taking of many samples or data points, and requiringan inordinate amount of time or number of sensors to completely inspecta structure.

As a result of the various practical difficulties outlined above, theprior devices described above have generally seen insignificantcommercial implementation despite the long-felt need for nondestructivetermite and wood-destroying insect detection. There is still a need fora nondestructive, reliable and easy-to-use apparatus and method fordetecting wood destroying insects.

SUMMARY OF THE INVENTION

The present invention is an apparatus, system and method for reliably,rapidly and easily detecting the presence of termites and other wooddestroying insects by nondestructive means. The present inventionincludes apparatus for detecting insect sounds over the full range offrequencies from about 100 Hz to about 15 kHz. The apparatus is capableof comparing the detected sounds to a library of previously recordedknown termite sounds, using pattern matching or recognition to findmatches. The apparatus is also capable of generating and transmittingdetection messages to an operator based on the results of thecomparison.

The apparatus may include an acoustic sensor, specially optimized fordetecting termite sounds in the 100 Hz to 15 kHz frequency range whileexcluding the effect of ambient noise. The sensor generally includes ahighly sensitive electronic microphone coupled with a mechanical soundamplification means, such as a stethoscope. The mechanical amplifierprovides the microphone with a signal having a high signal-to-noiseratio. The microphone then converts the high-quality sound signal to anelectronic signal, which can then be used for automated comparison. Thesensor may be filled or surrounded by a sound attenuating substance orelement for minimizing or eliminating the effect of airborne ambientsounds.

The invention may further include an acoustic pattern recognition systemincluding a prerecorded library of termite activity sounds for variousspecies of termites. This library serves as a reference of databasewhich may be compared with the newly detected and potential termiteactivity sounds by a processor included with the apparatus of thepresent invention. When the comparison achieves a certain predeterminedthreshold of similarity, the processor generates a “Termite Detected”message, which may be transmitted to the operator. Otherwise a “NoTermite Detected” message is generated and transmitted. The acousticpattern recognition system of the present invention not only can be usedto detect and identify termite infestation but also can be used todetect and identify other insect infestations by simply replacing thetermite database library with other appropriate insect databaselibraries of interest.

The acoustic detection method and system of the present invention mayalso be combined with an infrared detection system. Infrared detectionhas the advantage of covering a much larger area than acoustic detectionand, although less specific or accurate than acoustic detection,provides efficient screening and a convenient way of scanning thestructure for potential infestations in order to guide placement ofacoustic sensors in order to carry out more specific test with theacoustic sensors. In this way, inspection time requirements, and,therefore, costs, are greatly reduced. Further, detection accuracy isgreatly increased. The combination of infrared and acoustic inspectioncouples a quicker but low-specificity screening technique for speed witha high-specificity, slower technique for accuracy and is a significantimprovement in the art having important commercial applications.

This invention provides a method to detect wood destroying insectinfestation sites in a structure by performing a thermal scan of thestructure to identify potential infestation sites; positioning acousticsensors at the potential infestation sites to detect vibration signalsbetween 100 hertz and 15 kilohertz; transmitting detected vibrationsignals to a computing device for comparing the detected vibrationsignals with control signals; and detecting wood destroying insectinfestation if detected signals are substantially similar to the controlsignals.

Additionally, this invention provides a system to detect wood destroyinginsect infestation in a structure made of means to perform a thermalscan of a structure to locate potential infestation sites; a means toacoustically detect termite activity sounds at potential infestationsites; a means to compare detected termite activity sound, with alibrary of prerecorded termite activity sounds; and a means to determineif detected termite activity sounds are substantially similar toprerecorded termite activity sounds.

This technique is very effective in detecting both subterranean termitesand dry-wood termites. When a subterranean termite invades a structure,it brings in a substantial amount of moisture to the infested area. Asthe water (moisture) evaporates, the infested area becomes cooler, andthe difference in temperature can easily be detected by the thermalimaging camera, thus identifying a “suspicious area” of possiblesubterranean termite activity. However, as its name implies, thedry-wood termite does not bring in moisture to the infested area. Butdry-wood termites can still be detected by thermal imaging. Dry-woodtermites create a larger cavity in the infested wood object as comparedto subterranean termites. These large cavities are often carved out justbeneath the wood object's surface, without exhibiting any signs ofdamage to the surface itself. Therefore, it is extremely difficult tolocate these large cavities carved out by dry-wood termites. However,with the aid of a heat source these cavities can be detected by thermalimaging. The procedure involves exposing the targeted wood object to aheat source, such as an electric, gas or kerosene heater, an infraredlight source or any other kind of heat source. The wood surface abovethe dry-wood termite gallery cavity will possess a much lower heatcapacity as compared to the surrounding solid (cavity-free) wood. As aresult, the surface temperature above the cavity where the infestationis occurring will reach a higher temperature quicker than the surfacetemperature of the surrounding solid wood. This temperature differencecan be easily picked up by a thermal imaging camera and identified as a“suspicious area.”

One implementation of the invention is a method involving the placementof acoustical sensors on walls and other exposed portions of astructure, such as roof trusses. Signals from the sensors arecommunicated to a centrally located computing device including aprocessor. The processor analyzes the signals, preferably in the timedomain, for patterns characteristic of termites or other wood-eatinginsects. Upon detecting the presence of termites, the controller canthen generate certain kind of acoustics vibrations to repel thetermites.

According to yet another aspect of the invention, the sounds andlocation data taken at each inspection site using the above-summarizedmethods and apparatus, as well as data provided by other availablesources, may be provided to a central operations unit for use inbuilding a central database of termite information. The centraloperations unit may operate on a nationwide or even worldwide basis andserves as a facility of data communications, data acquisition,maintenance of sound libraries, continuous updating of sound libraryreferences, aggregation of recognition results and aggregation ofinspection results. The accumulated data may be made available toentities interested in termite presence, behavior, movements and trendsor in termite infestation and damage to structures, for access bystructure, species or geography, thereby providing an invaluable termiteinformation resource.

It is, accordingly, a first advantage of the invention that anondestructive and yet reliable method and apparatus for accuratelydetecting the presence of termites very quickly is provided.

It is a second advantage of the invention that a termite detectionmethod that utilizes nondestructive acoustic detection, that is carriedout in the full termite noise frequency range of 100 Hz to 15 KHz, andthat does not require on-site monitoring or interpretation of theacoustic detection results by a human operator is provided.

It is a third advantage of the invention that a termite detection methodthat utilizes nondestructive acoustic detection and yet that minimizesthe number of acoustic sensors, sample sites and time required toinspect a structure is provided.

It is a fourth advantage of the invention that a central database oftermite information, made available to appropriate entries andindividuals, is provided.

The acoustic detection system of the present invention enables thedetection of termite infestation in buildings and trees accurately andas early as possible. Early and accurate detection of an infestationreduces damage and the resultant amount of insecticide use required tostop it. By using acoustic detection, little to no damage to buildingsor trees occurs during the inspection process, therefore reducing theamount of money spent by the homeowner on repair work as well asreducing the risk of a lawsuit by the homeowner.

This invention further relates to the use of a laser doppler vibrometerto detect vibration of an unexcited wall, tree or other concealingstructure. In particular, this invention involves use of a laser Dopplervibrometer to detect acoustic patterns following acoustic excitation ofthe structure being evaluated, using apparatus and techniques similar tothose described in detail in U.S. Pat. No. 6,081,481, hereinincorporated by reference.

A still further aspect of the preferred embodiment of the invention ismodification of the behavior of detected termites using acousticsignals. The goal of such behavior modifications is to either repel thetermites, induce them to enter a trap where they can be destroyed, orotherwise cause the termites to behave in a self-destructive manner.

Finally, according to yet another aspect of the preferred embodiment ofthe invention, the sounds and location data taken at each inspectionsite using the above-summarized methods and apparatus, as well as dataprovided by other available sources, may be provided to a centraloperations unit for use in building a central database of termiteinformation. The central operations unit may operate on a nationwide oreven worldwide basis, and serves as a facility of data communications,data acquisition, data analysis, maintenance of sound libraries,continuous updating of sound library references, aggregation ofrecognition results, and aggregation of inspection results. Theaccumulated data may be made available to entities interested in termitepresence, behavior, movements, and trends, or in termite infestation anddamage to structures, for access by structure, species, or geography,thereby providing an invaluable termite information resource. No suchcentralized resource is currently available.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a termite detection systemassembled in accordance with the principles of a preferred embodiment ofthe invention.

FIG. 2 is a schematic illustration of a central computer with a termiteactivities sounds database library.

FIG. 3 is a schematic illustration of a combination of multiple acousticsensors and pattern recognition processor deployed in a structure.

FIG. 4 is a schematic depiction of an improved acoustic sensor accordingto the present invention.

FIG. 5 is a schematic depiction of another embodiment of an improvedacoustic sensor according to the present invention.

FIG. 6 is a flow chart depiction of the pattern recognition softwarealgorithm.

FIG. 7 is a schematic illustration of the termite detection process.

FIG. 8 is a schematic illustration of a structural integrity evaluationmethod diagram of a system for nondestructively evaluating structuraldamage in accordance with the principle of this invention.

FIG. 9 is a schematic illustration of the termite damage in tree anddetection/evaluation using LDV.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As schematically depicted in FIG. 1, a preferred embodiment of theapparatus and method of the present invention includes a thermal imagingcamera 1 for performing a preliminary scan of a structure 13 in order tolocate potential termite infestations sites 3. The structure 13 can be awooden object, such as a wall stud, paneling or in one embodiment a livetree. Termite infestation sites 3 can be the result of subterraneantermite or dry-wood termite activity. In the case of a subterraneantermite infestation, the moisture brought in by the subterraneantermites will show up as a “suspicious cold or hot spot” in a thermalimaging scan. In the case of a dry-wood termite infestation, a heat orcold source 9 is needed to increase or decrease the temperature of atargeted structure 13. This heat source 9 can be an electric, gas or oilheat source as well as an incandescent or infrared light source. Theareas in the targeted structure 13 that contain a cavity created bydry-wood termites will show up as “suspicious warm or hot spots.” Thecorrespondent video images of the potential termite infestation arerecorded by the camcorder 2 or by the thermal imaging camera if it isequipped with recording capability 6.

Upon a preliminary thermal indication of termite infestation observedwith thermal imaging camera 1, acoustic sensors 4 are positioned on thewall of the structure adjacent to the potentially infested locations inthe structure 13. The outputs of sensors 4 are passed through controller8, which includes a low-noise amplifier and a band-pass filter arrangedto exclude background noise and vibration signals below 100 hertz, andhigh frequency noise above 15 kilohertz and recorded by camcorder 2 orother audio recording device 6. A headphone 5 can be used to detectsounds and to facilitate the placement of the sensors 4. The recordedaudio information is then provided as an input to computing device 10,depicted in FIG. 2, for analysis of the detected noises. The computingdevice 10 in FIG. 2, which is typically centrally located but may alsobe portable, is operably connected with a database library (controlsignals) 11 of termite sounds for comparison with the detected vibrationsignals, as further described herein below. The wood destroying insectinfestation sites 3 is detected if the detected vibration signals aresubstantially similar to the control signal.

Thermal imaging camera 1 may be any of a number known, commerciallyavailable infrared cameras conventionally used by structural engineers,police and the military. In order to improve the accuracy by which thethermal imaging camera 1 detects potential areas of termite infestation,the thermal imaging camera may further include wood destroying insectinfestation recognition software, such as matched filtering softwarewhich compares the frequency spectrum of a thermal image with frequencyspectra of a reference images known to indicate termite infestation,thereby reducing the level of skill required of the camera operator,reducing time required and increasing termite identificationeffectiveness. This database of infestation images of suspicious thermalimages can be built by one skilled in the art.

Controller 8 includes a low-noise amplifier and a band pass filter. Theband pass filter preferably has a pass band, for most species oftermites, of from between 100 Hz to about 15 kHz. Controller 8 may be aseparate unit or may be included, in whole or in part, in the acousticsensors.

Database library 11 is made up of a compilation of numerous termitesound recordings in different settings, substrates and conditions,collected and catalogued over a period of time. The system and apparatusof FIG. 1 may be used to capture and compile recordings of termitenoises in one setting that can be used as controls for comparison withactual detected noise patterns. The controls included in databaselibrary 11 may include sounds from different species of termites invaried environments and under varying conditions to account for theexpected degree of variation in termite sounds that may be encounteredbased on these variables.

A processor in computing device 10 compares the recorded signals fromcontroller 8 with the signal patterns stored in database library 11.When the comparison achieves a certain predetermined threshold ofsimilarity, a “Termite Detected” message will be generated andtransmitted to the operator; otherwise, a “No Termite Detected” messagewill be generated and transmitted to the operator.

Due to advanced computing technology the above operation can also beeasily performed by a mini PC which can be easily attached or built intothe controller 8.

It will be appreciated by those skilled in the art that the acousticpattern recognition system not only can be used to detect and identifytermite infestations but can also be used to detect and identify otherinsect infestations by replacing or supplementing the database library11 with sounds recorded from other insect infestations.

The acoustic pattern recognition method described above may be used toprotect, through early detection, buildings or any other wood structuresfrom termite invasions even before any signs of termite infestation arevisible through use of the thermal imaging camera 1 and acoustic sensors4. (The term “structures” is intended to encompass natural as well asmanmade victims of termite infestation, including trees.) Asschematically depicted in FIG. 3, this protection is achieved bypermanently deploying an array of acoustic sensors 4 on all majorbuilding structures 13 such as trusses, studs and joists, and byconnecting the sensors to a central controller 8. Signals picked up byany sensor 4 are passed through an electronic circuit in centralcontroller 8, which includes a low-noise amplifier and a band-passfilter arranged to exclude background noise and vibration signals below100 hertz, and high frequency noise above 15 kilohertz. The processedsignals are then converted into digital signals for processing by aprocessor 12 contained within central controller 8. The processorcompares the signals with the pre-recorded data from insect databaselibrary 11, to which central controller 8 is electrically operablycoupled. When the comparison achieves a certain pre-determined thresholdof similarity, a “termite invasion” warning signal may be generated andissued to the home or building owner or to a contract securitymonitoring system, or simply generate acoustic vibration signal on thestructure to repel invading termite. Acoustic vibration signal can begenerated by small transducers (commercially available) that arepermanently attached to building structure such as trusses, studs, andjoists.

While the present invention is not limited to a particularpattern-matching algorithm, there are various techniques that arecapable of identifying an insect acoustic signal and that are suitablefor use with the present invention. For example, a cross-correlationalgorithm, although not the fastest algorithm available, has shown goodconsistency and accuracy. Cross-correlation works best when the insectsignal is louder than the background noise. Of course, as will beappreciated by those skilled in the art, any other suitable techniquemay be used to extract acoustic signals that are embedded in thebackground noise level.

The acoustic sensor 4 employs a sensitive microphone 40, which isembedded in a stethoscope 46. The output electrical signal frommicrophone 40 is sent through coaxial cable 41, which is electricallycoupled to controller 8. Stethoscope 46 is employed because itsmechanical amplification characteristic produces a very highsignal-to-noise ratio output.

The illustrated embodiment of sensor 4 includes a long (6″ to 12″) smalldiameter (10 to 16 gauge) spike 44. Proximal end 62 of spike 44 is inintimate and integral contact with the stethoscope diaphragm 42. Distalend 64 of spike 44 may be used as a probe that can be inserted intopotential infestation areas such as walls, wood members, cracks, baseboards, trees, etc. It is critical that spike 44 be flexibly but firmlyconnected at connection 43 to rigid face plate 45 of the sensor unit 6so that sound vibrations in spike 44 are not attenuated by face plate45, but also so that spike 44 has the required degree of rigidity forinsertion into hard material. Connection 43 may be made by riveting orby any other similar method of connection that provides a firmconnection and yet does not integrally connect spike 44 with face plate45 and allows for a small degree of relative movement between the twostructures. This will ensure that most of the structure-borne signalswill transmit through spike 44 to stethoscope diaphragm 42 and yet spike44 will have enough mechanical support strength from the faceplate toallow insertion into wooden objects.

Stethoscope 46 serves to mechanically amplify the signal, whichprimarily includes termite structure-borne signals, transmitted fromspike 44 to diaphragm 42. The sounds detected by spike 44 and diaphragm42, then amplified by stethoscope 46, are converted by microphone 40into an electrical signal that is transmitted through coaxial cable 41to the controller 8. Alternatively, other transmission media may beused, such as light transmitted over optical fiber. Face plate 45 andsensor housing cap 48 are sealingly attached at periphery 49 or securedby a treaded ring to housing cap 48 periphery (treaded) 49. The bulk ofairborne background noise that might interfere with termite detectionaccuracy is eliminated by this sealed housing. Further, housing cap 48and face plate 45 together serve to form a sealed, protective enclosurefor the internal sensor components. Face plate 45 may be made of metal,preferably mild steel, and about 26-28 gauge thickness. Housing cap 48may be of metal about the thickness of face plate 45 or of thickerplastic. Space 47 between stethoscope 46 and cap 48 may be filled with anoise-attenuating medium such as modeling clay, acoustic absorbingmaterial, etc.

FIG. 5 depicts another embodiment of acoustic sensor 4. While similar tothe sensor depicted in FIG. 4, spike 44 has been replaced with a smallerdiameter variable length disposable probe 50, similar to a disposablehypodermic needle. The disposable probe 50 can be easily connected to areceptacle connector 51, which may be a “Lauer lock” connector. Theprobe 50 and receptacle connector 51 are tightly secured to face plate45, preferably by strong glue at connection 52, so as to ensure thatprobe 50 is firmly supported while the proximal end 72 maintainsintimate integral contact with diaphragm 42. Through this arrangement,probe 50 and receptacle connector 51 function as a “fixed” probe thatcan transmit most of the structure-borne termite signals to thestethoscope diaphragm.

As an alternative to the embodiments described above wherein anacoustical sensor is used to sense termite sounds, termite soundvibration may also be detected by other vibration sensing means. Suchmeans may include, for example, an accelerometer.

According to an especially advantageous aspect of the preferredembodiment of the invention, computing device 10 as depicted in FIG. 2may be part of or can be interconnected to a nationwide or evenworldwide operations center that may serve as a facility for datacommunications, data acquisition and data analysis. Database library 11may be maintained at this centralized location and may be continuouslyupdated based on recorded sounds received from a wide variety oflocations and under a wide variety of conditions. The centralized natureof compilation enables aggregation of recognition results andaggregation of inspection results. The resulting database or databases11 may include the above-mentioned libraries of termite sound and/orresponse data as well as other types of termite data or information, foruse by any individuals or entities interested in termite presence,behavior, movements and trends, as well as those specifically concernedwith termite infestation and damage to structures. Access to thedatabase may be by structure, species or geography or any otherappropriate category or classification. Portable computer units couldcontain databases that receive periodic updates to provide instantfeedback while maintaining mobility.

As depicted in FIG. 6 flow chart of the pattern recognition process, theprocess has three stages. In the Recording stage, suspicious sounds aredetected by the acoustic sensor and fed into the computer, where thesounds are then recorded by the pattern recognition software. After thesounds have been detected and recorded, the Chopping stage beginswherein the pattern recognition software measures the incoming acousticsignals and compares them to signals determined to be background noise.If the detected signal is determined to be louder than the backgroundnoise level, the software then ascertains the signal's length. If thesignal is determined to have a length between 0.5 millisecond and threemilliseconds (which is unique characteristics of termite activitysound), the signal is then passed along to the Cross-Correlation stage.In the Cross-Correlation stage, the software compares the detectedsignal to prerecorded termite activities signals contained in thedatabase library 11. A certain degree of similarity indicates that thedetected signal matches a pre-recorded signal or signals found in thedatabase library, and it is determined that a termite has been detected.If an insufficient degree of similarity is found between the detectedsignal and prerecorded signals in the database library, the softwaredetermines that no termite has been detected. A sample of this type ofsoftware is set out in appendix A (hereby incorporated by reference).

Termite Detection Pattern Recognition Algorithm

The termite detection algorithm consists of three main tasks: Recording;Chopping; and Cross-correlation, as set out in FIGS. 6-7.

These tasks take place sequentially in the order above once the userclicks the “Detect” button of the operational pop-up menu as seen on themini-computer in order to activate the pattern recognition software.

The tasks execute independently from one another, but the input at stage“i” depends on the output of the previous stage “i−1”. The Choppingstage depends on the Recording stage. The Cross-correlation stage isreally independent of the Chopping stage, but detection accuracyimproves when Chopping is performed before Cross-correlation.

The detection process is depicted above, and can be summarized asfollows:

-   -   (a) The Recording stage captures an audio signal from an        external source (suspicious termite sound source 3) by an        acoustic sensor.    -   (b) The Chopping stage receives the recorded signal as input and        produces N numbers of chopped signals.    -   (c) The Cross-correlation stage receives the N chopped signals        plus M additional audio signals previously stored in a database        (prerecorded termite signal). From these signals N×M        cross-correlation values are calculated.    -   (d) The cross-correlation values are non-dimensional real        numbers that give a good estimation of how close the N signals        taken from the external source “match” the signals stored in the        database (perfect mach will produce a value of 1). Recording    -   (e) In the Recording stage, an audio signal is recorded from the        suspicious source, converted and stored in digital form to the        computer.

The signal is acquired at a rate (sampling rate) of 44.1 KHz (44,100points per second) or higher, with a resolution of 16 bits or higherthrough a single channel. In the current implementation the signal isrecorded for five seconds (can be shorter or longer), after whichRecording ends and the next stage Chopping starts. On the Windowsdesktop platform, recording is implemented using the MMIO (MultimediaI/O interface). On the Pocket PC platform, it is implemented by reusingthe embedded Voice Recorder Control, with the AGC (Automatic GainControl) turned off.

In the chopping stage, the recorded signal is processed and cut insmaller chunks; N shorter signals are created, or fewer, depending onthe original signal. The chopping process works as follows. First, thenoise floor level of the input signal is calculated. This is done byaveraging the maximums of the signal and multiplying the result by acorrection factor. Second, the input signal is scanned until the firstmaximum that exceeds the noise threshold is found. All samples scannedbefore the first maximum is discarded. Third, the signal is furtherscanned until the next maximum below the noise threshold is found. Ifthe duration is between 0.5 to three milliseconds apart from the firstmaximum, the signal is chopped and captured as potential termite sound.Otherwise, the samples are discarded. This follows from the fact thattermite sounds have very short duration, longer signals have littlechance of belonging to termite sound sources. The process continuesuntil the whole recorded signal is consumed.

In the cross-correlation stage, the N individual signals received fromthe chopping stage are “cross-correlated” with M fixed signals from thepreviously recorded known termite sound application database. Thisinternal database is called the “termite database”. Thecross-correlation between two signals A and B provide a measure of howclose signal A matches the shape of signal B. With this in mind theprocess works as follows. First, the chopped signals arecross-correlated one by one with each signal from the termite database.Second, the cross-correlation value is compared against across-correlation threshold. If the calculated value exceeds thepredefined threshold, a match occurs indicating detection. The processstops. Third, if the calculated value is below the cross-correlationthreshold, the chopped signal is discarded. The process continues untilall chopped signals are cross-correlated with the database signals oruntil a successful match occurs, whichever comes first.

In another aspect of this invention shown in FIG. 8, a method forevaluating potentially damaged concealed in a structure 13. Theillustrated arrangement employs a vibration-inducing device or shaker 62and a laser vibrometer 60 for measuring the resulting vibration pattern,which depends on the integrity of the structure being analyzed. Thevibration inducing device 62 induces a broadband frequency vibration inthe structure. Different construction and conditions of the structurerespond differently to the induced vibration, causing reflectionsbetween areas of different impedance and resulting in a unique vibrationpattern. The vibration patterns can then be easily picked up by thelaser vibrometer 60 and analyzed according to the principles set forthand herein specifically incorporated U.S. Pat. No. 6,081,481.

Another aspect of the preferred embodiment of the invention is the useof acoustic stimuli to change the behavior of termites. This aspect ofthe invention essentially involves exposing termites to various soundsand determining the reaction of the termites to the sounds under variousconditions. For example, certain sounds cause termites to feed, andothers appears to function as a warning signal which causes the termitesto stop feeding.

The acoustic behavior modification aspect of the preferred embodiment isbased on discoveries relating to the manner in which termites recognizeand react to sounds, and in particular their ability to sense subtlevibrations in a structure by means of the sensory hairs that are foundall over the body parts of termites. These sensory hairs vary in sizefrom a few microns up to hundreds of microns. Because these sensoryhairs on the legs are directly associated with the nervous system, whenthe sensory hairs on the termite's legs come in contact with a substratesurface, the termite is capable of picking up and responding to veryminute substrate vibrations.

Preliminary tests have shown that when a termite was secured to a verysmall and light weight fixture with two micro electrodes, one insertedinto the nervous system right next to the base of one of the six legs,and the other inserted into another part of the body, the two microelectrodes formed a closed electrical circuit, and that when acousticalvibrations were introduced to the termite, certain physical and nervousresponses were invoked. The nervous responses were in the form ofelectrical signals, which were clearly picked up by the microelectrodes, while the physical responses were displayed through the aidof a microscope and CCD video camera.

Armed with this understanding of acoustic responses, the skilled artisancan, in principle, use the acoustic signals to alter the termite'sbehavior, creating a nonchemical acoustical barrier to keep termites outof a building, make chemical bait more attractive to termites, orpossibly even trigger a self-destruct process in the termite colonies.

This method to disturb insect infestation behavior can be adapted by oneskilled in the art to apply to fire ants, carpenter ants, carpenterbees, and wood boring beetles.

More specifically, a structural borne acoustic vibration is produced bya vibration inducing device 62. The characteristics (frequency andamplitude) of the vibration are dependent on the type of structure andthe location of the insect. In the preferred embodiment the vibration isa pattern of vibrations which can be modulated. This structural borneacoustic vibration has been shown in laboratory experiments to disturbinsect infestation behavior. In particular, the structural borneacoustic vibration has a frequency of between 100 Hz to 4000 Hz and anamplitude as low as 2×10⁻⁸ displacement and has been shown to disturbthe infestation behavior of termites and fire ants.

Now referring to FIG. 9, a vibration inducing means 62 such as a hammeror a shaker, is used to induce vibration in a tree. A laser dopplervibrometer 60 is used to detect changes in the vibration patternreflected by a structure such as a tree. If a tree is damaged by wooddestroying insects, the vibration pattern differs from an undamagedtree.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it will be obvious that certain changes and modificationscan be made which are within the full scope of the invention.

1. An acoustical sensor for detection of insect infestation in aresidential structure comprising: (a) a sealed chamber includinginternal sensor components, said internal sensor components comprising:a diaphragm configured to detect structure-borne sound; a means tomechanically amplify the sound produced by said diaphragm; a means toreceive airborne sound and to convert said sound to an electrical signalwherein said sealed chamber is configured to maintain signal integrity;and (b) a detection member having a proximal and a distal end, saidproximal end contacting said diaphraam and said distal end configured tobe inserted into a potential infestation site without damaging saidresidential structure.
 2. The sensor of claim 1 wherein said detectionmember is a spike permanently attached to said sensor, wherein saidspike is between 10 to 16 gauge in diameter.
 3. The sensor of claim 1wherein said detection member is a probe reversibly attached to saidsensor, wherein said probe is between 10 to 16 gauge in diameter.
 4. Thesensor of claim 1 wherein said means to mechanically amplify the soundis a stethoscope.
 5. The sensor of claim 1 wherein, the means to receiveairborne sound and to convert said sound to an electrical signal is amicrophone.
 6. A method of collecting data concerning termites,comprising the steps of: (a) inserting a distal end of a detectionmember of the acoustical sensor of claim 1 into a residential structure;and (b) detecting signals from said sensor to collect data; (c)transmitting data collected by the sensors to a central operationscenter for inclusion in a central database of termite data.
 7. A methodto detect wood destroying insect infestation of a residential structurecomprising: (a) affixing a distal end of a detection member of theacoustical sensor of claim 1 to portions of a residential structure; (b)transmitting signals from said sensor to a computing device; (c)comparing detected signals with control signals; and (d) detecting wooddestroying insect infestation of said residential structure if saiddetected signal is substantially similar to said control signals.
 8. Themethod of claim 7 wherein said detection vibration signals are between0.5 and three milliseconds in length.
 9. The method of claim 7 whereinsaid computing device is a central processor.
 10. The method of claim 7wherein said computing device is a hand held process.
 11. The method ofclaim 7 wherein said wood destroying insects are termites.
 12. Themethod of claim 7 wherein the control signal stored in the computingdevice is modified to include the detected signals.
 13. The acousticalsensor of claim 1 wherein said detection member is between 6 to 12inches in length.